Efficient utilization of red mud waste via stepwise leaching to obtain α-hematite and mesoporous γ-alumina.

Utilizing the red mud sustainably is now a challenging issue. Red mud due to its wide production, presence of some radioactive elements, high alkalinity, and salinity, has a dramatic potential to contaminate soil and groundwater. Notwithstanding its drawbacks, Red mud consists several elements, including Ca, Al, Ti, Si, and Fe, in various mineral forms. In this study, stepwise leaching was applied as a proper method to separate and purify the main valuable elements using available and affordable HCl. The pre-leaching step under optimized conditions using HCl (0.2 M) at room temperature for 2 h removed 89% of the calcium content from red mud. To selectively remove the solid silica, the residue was treated with concentrated HCl (3.0 M, L/S of 20 mL/g) at 95 °C, resulting in the dissolution of iron and aluminum content with up to 90% efficiency. After precipitation of the Fe

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